Generally, as a system for directly mounting semiconductor chips (hereinafter sometimes simply referred to “chips”) on a circuit board in accordance with a face-down bonding system, a system in which solder bumps are formed on electrode portions of semiconductor chips, which are connected to a circuit board by soldering, and a method in which a conductive adhesive is applied to protruding electrodes provided to semiconductor chips for electrically connecting to circuit-board electrodes, are known.
These systems have problems. When a chip and a board are exposed to various environments, stress is produced in the connection interface ascribed to a difference in thermal expansion coefficient between the chip and the board to be connected, with the result that connection reliability decreases. Therefore, in order to reduce the stress in the connection interface, a system for filling the gap between the chip and the board generally with an underfill material such as an epoxy resin has been studied.
As a filling system with the underfill material, mention may be made of a system in which a chip and a board are connected and thereafter a low-viscosity liquid resin is injected and a system in which an underfill material is placed on a board and then a chip is mounted. In the meantime, as a method in which an underfill material is previously placed on a board and then a chip is mounted, a method of applying a liquid resin and a method of attaching a resin film are known.
However, in the case of applying a liquid resin, it is difficult to accurately control the application amount by a dispenser. In the context of a recent tendency toward thin-film chip, the resin, if excessively applied, runs off from a chip in a bonding process, moves up along the side surface of the chip and contaminates a bonding tool. Because of this, a tool washing step must be added, complicating a process at the time of a large-scale production.
Alternatively, in the case of bonding a resin film, it is easy to supply an optimum amount of resin by controlling the thickness of the resin; however, when the film is bonded to a board, a step of bonding the film called a provisional pressure-bonding step is required. In the provisional pressure-bonding step, a reel tape having slits at the intervals larger than the width of a target chip is used. The adhesive present on the base material of the reel tape is cut in half depending upon the size of the chip and bonded to the board by thermocompression bonding at such a temperature that an adhesive does not react.
Since the accuracy of supplying the film to a chip mounting position is low, generally a larger film than a chip size is bonded in the provisional pressure-bonding in order to keep yield. Accordingly, enough distance is required to an adjacent component, impeding high-density packaging. On the other hand, thin-width reel processing dealing with microchips, etc. is difficult. It is still necessary to bond a larger film than a chip size to deal with this case. An extra mounting area is required.
In the context, a method for supplying the same-size adhesive as a chip size is proposed. In this method, an adhesive is supplied in the stage of a wafer and then processed simultaneously with chips by dicing or the like to obtain chips attached with the adhesive (see, for example, Patent Documents 1, 2).                Patent Document 1: Japanese Patent No. 2833111        Patent Document 2: Japanese Patent Application Laid-Open No. 2006-049482        